I think B/W is fine.I have the Humminbird 597ci di and it works great for this purposes. I still haven't been brave enough to venture out past the flats and shallows so the sonar is mostly used to locate and stay on drop offs. It's been pretty useful in that regard - next season I plan on trying to locate some structure in deeper waters and try my hand at grouper fishing or use the sonar to locate schools of bait fish and give king macks a try.

Most useful aspects of the fish finder is the water temp readings and the GPS for shallow water. For this purpose, black and white is just fine.